Amp Purchase advice?

Hiya!
Since everyone here has been super helpful, I wanted to ask for advice on purchasing a dedicated headphone amp.
I currently use the Dragonfly Red as a DAC/Amp at work, and while I love it I think I could probably get better sound by using the Dragonfly as dedicated DAC and running it into a standalone headphone amp.
My main set of headphones are Beyerdynamic T1 2d gens. I will probably also use the amp to power my Hifiman 4XX and Sennheiser 6XX.
My budget is flexible, part of my question is whether its worth it to invest big money (over $600) in an amp -- the consensus is that there are diminishing returns.

There seems to be a lot of positive buzz on this amp but I think I just need an amp, not a dac/amp hybrid. I'm a bit concerned about getting another DAC because I can't install device drivers on my work computer

You don’t have to spend big money for a great amp, Magni 3 would be perfect for you. Has a slightly warm tilt, 430mw @ 300 ohms which plays the 6XX really loud, then if u want, buy a modi multibit for a terrific DAC and for 350$ u got a killer system.

I actually had a talk with some people recently, and we were actually somewhat stumped. It's surprisingly hard to find a variety of amps with under 1 Ohm output impedance under 500 dollars(ideally close to 0). You've got O2, Schiit Magni 3(And Jotunheim) , Arcam rHead, and JDS Labs EL Amp/Element. A lot of other stuff runs 1-2, and then a lot of chinese stuff runs around 10. Most of the cheaper things run like 2-3, and some of the really cheap stuff run like 15. Is this bad? Not for a huge majority of headphones.
What do you want in an Amp? At that money you can start into some of the well liked tube amps if you want a different sound signature, you can get a pretty decent solid state amp. If you budget well, you could get a decent solid state amp and a tube amp. Is it about power? Is there a sound signature you want?

Hi,
Thanks so much for your response!
What do I want in an amp? Mostly just something that plays nice with my current roster of headphones -- I don't think there is a particular sound signature I'm seeking above others, although my listening tastes tend toward bass-heavy genres like hip-hop, r&b, electronic, rock, etc. (I don't listen to a ton of classical)
Just for the purposes of education (I'm new here), why is it important to find an output impedance under 1 Ohm?

It's really not. Lower is better, but as long as it's under like.. 3-4, it's fine for most lower ohm headphones. You want ideally a 1/8th of your headphone's impedance or less for your output impedance, not counting planars like the 4XX you have, otherwise it can color the sound or add distortion to your headphones. This is mostly for solid-state amps. It's not important to be under 1 ohm, but there are some super sensitive 8-ohm IEMs for example. And 16-20 ohm headphones aren't terribly uncommon, so under 2 is sort of the ideal to be able to drive ANYTHING without distortion. 3 ohms will be okay for most things. Once you get to about 4-5 it might start affecting you a bit.
You might like tubes if you like warm sound signatures. Though tubes can get REALLY in depth and different tubes can change the sound from an amplifier though, so depends on how much you want to try tweaking the sound with tube-rolling as well. I've never gone tubes myself, so I can't really suggest anything on that side.
I personally am planning to pick up an EL Amp or Element myself in the future(Element has a built in DAC for 70 more). It's not the most amazing price/performance, but it's a solid single-ended amplifier that looks incredible.
The hardest to drive thing you have looks to be those Beyerdynamic T1. Pretty much any of the amps I mentioned before should have more than enough juice for those though.

If you could find a Gustard H10 its a very nice solid state amp, it works really well with the DFR in line out mode, especially once you replace the stock opamps for Burson V6 ones (pair of Vivid singles and pair of Classic duals). It's an extremely nice warm leaning amp that drives an HD6XX very well and for ~$300 +$200 for the opamps is really something special.
I will say though it really needs cooling mods, at minimal heatsinks on the two voltage regulators and venting of the top cover. If you are not prepared to mod then I would look elsewhere. Compared to just the DFR it really brings the bass, gives noticeably better dynamics, detail, and more clarity with smoother highs.

search

The Burson opamps:

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The red opamps are the Burson V6 Vivids and the orange the V6 Classics:

thanks for all the tips! This is very helpful, although I'm a little bit gun shy about doing a lot of DIY circuit modification. however, if I can get a great amp with ~200 plus modifications on eBay, it might be worth the effort.
Have you heard anything about the Gustard H20? I saw it dropped here a little bit back, but I missed out.

All the mods I did were thermal/mechanical, didn't change anything with regards to the stock electronic board circuit - the opamps plug into 8 pin socket connectors on the board. Heat sinks were selected and adhered to the transistors that needed them.
The reason I ended up choosing the Gustard H10 was actually got a Massdrop email about a drop for it and then researched it. This was after hearing high current amps at a headphone meet with my TH-X00PH and M1060 and wanting to look into higher powered amps. Experimenting with opamps and being able to alter the sound with them was a big draw as was its really low output resistance and high praise of its dynamics, clarity, and detail with Burson opamps. The one thing that had me nervous was the heat related failure issues with the Burson V5 opamps... they simply were not reliable stuffed inside the closed H10 chassis and would fail from heat buildup. Decided to get the H10 anyways (bought 2 in the drop actually) with plans to mod it to reduce heat on the components, which is what I did. I ran it with the top off until the mods were completed so it would help out the two voltage regulators which were identified as the main components that needed some thermal help.
I was looking into the H20 as well, but it seems to have gone a different direction from the H10, with a different sound and not really designed for rolling opamps. Absolutely love the sound the H10 provides and will stick with it, it works great with all my dynamics and planars.
Whatever amp you go with I would suggest something on the warmish side that also is known for excellent detail, dynamics, and clarity. I previously thought that a neutral amp was my ideal, but the Meier Audio JAZZ-ff I had showed me that no matter how clear and detailed it was, it just didn't sync with me - my headphones always somehow felt lacking in bass presence/impact and dynamics. The H10 cured the lack of bass and dynamics for my phones while also adding in even more detail than I heard from them before.

Projecting my own ~$600 other people's money - wants here, thanks;) but it is a unique amp at the price range you are looking at; The La Figaro; https://www.massdrop.com/buy/la-figaro-339-tube-headphone-amplifier, on my list for an OTL.
Your post made me go look for a used one on eBay...:) then today it dropped here, coincidental... Would be a bit of an odd-fellows thing feeding it a Red Dragonfly, but hey make it your own, until you decide to upgrade the DAC. You will be blowing some more $ on upgrading tubes, but you can do that later, now you would have something unique and fun. It is not optimum for low impedance, but it still will push them just fine., your HD6XX's will simply elope.
Otherwise in SS amp/DAC world the TEAC 501 that was recently up on MD; https://www.massdrop.com/buy/teac-ud-501-dual-monaural-dac-amp would be a nice upgrade, and the Dragonfly remains your portable. On Amazon for a good price still; https://www.amazon.com/Teac-Monaural-Converter-Streaming-UD-501-B/dp/B00BC1ULTQ/ref=sr_1_1?ie=UTF8&qid=1519576653&sr=8-1&keywords=teac++501
Yes, the TEAC has them,I'm a MUSES fan: https://www.njr.com/MUSES/index.html
Love this post, funny, but there is truth in the musings... what happens in some semiconductor fabs, is like Vegas... it stays in the fab...
NJR is boutique, yes, better does cost more...
"Originally Posted by jcdriscJRC has chosen to wrap the die of each chip in a very rare silk thread only made in a small farm in Hokkaido. This accounts for their astounding sonic signature and increase in fiscal depletion of truly dedicated audiophools using them.
a japanese friend of mine said than :
"The silk thread is made by 30 years old Virgin Muses whom only eat Kobe beef, then are blessed in Greece after a Master in Harp playing for a better mature product! Education costs a lot ! Some even say than the oaps are brushed with beers while leads are sharpened by Fugu cooker Masters !
But mostly: due to a crisis to find ethiopian eunuchs for the quality control with the virgins production benchs, the prices as the panties have been soaring"
I believe him as he stoped to drink sake ! "
http://www.diyaudio.com/forums/analog-line-level/262261-jrc-muse01-muse02-opamps-expensive-2.html